pathy ... lest the term delude us into thinking that we understand what is going on." If increased capillary pressure is essential for red cell extravasation then it is possible that altered blood rheology is involved. During strenuous exercise stiffening of red cells induced by catecholamine occurs, and changed renal function results in high molecular weight proteinuria'° and haematuria4 in healthy subjects. It should be noted that IgA nephropathy is associated with both a high incidence of haematuria and altered blood rheology. 10 There are several published claims that phase contrast microscopy of urinary sediment can distinguish cells of "glomerular" origin from those of "non-glomerular" origin, but a study of the effects on the shape of red cells when normal blood was mixed with normal and pathological urine (Simpson, unpublished data) showed that glomerular type red cells were present at two minutes and persisted for 90 minutes. Small percentages of non-glomerular cells persisted throughout the study. Thus it seems that glomerular red cells are a response to the urinary environment. Although there may be good clinical reasons for measuring the red cell content of haematuric urine, it may be more diagnostically rewarding to determine whether or not there is an associated

haemorrheological abnormality. L 0 SIMPSON

Department of General Practice, Medical School, University of Otago, Dunedin, INew Zealand 1 De Caestecker MP, Ballardie FW. Unexplained haematuria. BMJ 1990;301:1171-2. (24 November.) 2 Birch DF, Fairley KF, Whitworth JA, et al. Urinary erythrocyte morphology in the diagnosis of glomerular haematuria. Clin Nephrol 1983;20:78-84. 3 Loh EH, Keng VW, Ward PB. Blood cells and red cell morphology in the urine of healthy children. Clin Nephrol 1990;34: 185-7. 4 Gibbs DD, Lynn KL. Red cell volume distribution curves in the diagnosis of glomerular and non-glomerular hematuria. Cln Nephrol 1990;33:143-7. 5 Ohsaka A, Suzuki K, Ohashi M. The spurting of erythrocytes through junctions of the vascular endothelium treated with snake venom. Microvasc Res 1975;1O:208-13. 6 Simpson LO. Basement membranes and biological thixotropy: a new hypothesis. Patholog.6 1980;12:377-89. 7 Simpson LO, Glomerular permeability-an alternative to the pore theory. Lancet 1981;ii:251-2. 8 Warfel KA, Hull MT. Migration of lymphocytes through the cutaneous basal lamina in normal skin. Anat Rec 1984;208: 349-55. 9 Anonymous. Thin-membrane nephropathy-how thin is thin? [Editorial]. Lancet 1990;336:469-70. 10 Shand BI. Studies on proteinuria in mouse and man [Dissertation]. Otago: University of Otago, 1982. 11 Shand BI, Bailey RR, Simpson LO. Blood rheology in IgA nephropathy. Clin Nephrol 1988;29:288-93.

AUTHORS' REPLY, -Questions regarding the pathogenesis of haematura and urinary red cell dysmorphism are important and warrant further consideration. It may, for example, be impossible to prove by direct observation the thesis that attenuation of basement membranes in thin membrane nephropathy accounts for the passage of erythrocytes from the capillary lumen into Bowman's space, but circumstantial evidence from .clinicopathological observations suggests that this represents a useful working hypothesis for the management of patients with unexplained urinary blood loss.' The proposals of permeabilisation of basement membranes dependent on pressure and flow may also explain these phenomena, but these too remain to be proved. The aetiology of urinary red cell dysmorphism in glomerular disease is also unclear. There are proponents of an osmotic urinary mechanism,' mechanical distortion,3 and both.' Indeed it is probable that the underlying process reflects a nonspecific response of the erythrocyte to a variety of extreme environmental stresses during its passage into and along the nephron. Dr Simpson's observation that dysmorphic "glomerular" red cells may

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be reproduced by simply mixing normal peripheral blood with normal or pathological urine is contrary to our own experience. This discrepancy probably results from differences in definition of glomerular as distinct from non-glomerular urinary red cell variants. It is also particularly important as Dr Simpson's observations suggest that this phenomenon may be purely artefactual, flying in the face of a large body of reports that substantiate the view that dysmorphic haematuria represents a characteristic feature of glomerular disease.2 50 This underlines the need to establish a simple, common classification for the microscopic assessment of urinary red cells. This would facilitate the objective comparison of published results from different centres and allow more hospital laboratories to adopt this technique as a non-invasive and low cost diagnostic aid. M P DE CAESTECKER F W BALLARDIE Manchester Royal Infirmary, Manchester M13 9WL 1 Glassock RJ. Through thick and thin. N EnglJ7 Med 1989;320: 51-3. 2 Birch DF, Fairley KF, Whitworth JA, etal. Urinary erythrocyte morphology in the diagnosis of glomerular haematuria. Clin Nephrol 1983;20:78-84. 3 Kubota H, Yamabe H, Ozawa K, et al. Mechanism of urinary erythrocyte deformity in patients with glomerular disease. Nephron 1988;48:338-9. 4 Kitamato Y, Chu YD, Tomita M, Nakayama M, Sato T. Reproduction of urinary dysmorphic red cells in vitro. Kidney Int (in press). 5 Rizzoni G, Braggion F, Zacchello G. Evaluation of glomerular and non-glomerular hematuria by phase contrast microscopy. J Pediatr 1983;104:370-4. 6 Fassett RG, Horgan B, Gove D, Mathew TH. Scanning electron microscopy of glomerular and non-glomerular red blood cells. Clin Nephrol 1983;20:11-6. 7 DeSanto NG, Nuzzi F, Capodicasa G, et al. Phase contrast microscopy of the urinary sediment for the diagnosis of glomerular and non-glomerular bleeding: data in children and adults with normal creatinine clearances. Nephron 1987;45: 35-9. 8 Pillsworth TJ, Haver VM, Abrass CK, Delaney K. Differentiation of renal from non-renal haematuria by microscopic examination of erythrocytes in the urine. Clin Chen 1987;33: 1791-5. 9 De Caestecker MP, Hall CL, Basterfield PT, Smith JG. Localisation of haematuria by red cell analyser and phase contrast microscopy. Nephron 1989;52: 170-3. 10 Schramek P, Schuster FX, Georgepoulos M, Papaczy P, Maier M. Value of urinary erythrocyte morphology in the assessment of symptomless microscopic haematuria. Lancet 1989;ii: 1316-9.

Selling tobacco to children SIR,-We fully endorse Dr Amanda Amos's call for government action to stop children smoking. Last year, on behalf of Oxfordshire Action on Smoking and Health, we surveyed five parishes in the county for adherence to the voluntary agreement on tobacco advertising. Comparison with data in the annual report of the Committee for Monitoring the Agreement on Tobacco Advertising and Sponsorship, a quango comprising tobacco industry representatives and civil servants, showed that Action on Smoking and Health submitted 51% of the complaints received and reported 50% of all breaches of both the voluntary agreement and the Advertising Standards Authority code. If our sample was representative there may have been over 50000 breaches of the code last year, mostly unreported, yet the Department of Health claims that the system is working (personal communication). Of even greater concern is the mass of tobacco promotional material that is exempt from the code. Striking examples are toy and model cars for children that bear cigarette brand logos and names. The monitoring committee has repeatedly been sent examples of such indirect advertising but claims that tobacco companies have no control over unauthorised use of their logos. Our mounting correspondence with the committee shows that the voluntary agreement allows more tobacco advertising than it restricts. This agreement has more holes than the

Jumblies' sieve and should be consigned to a book of nonsense. The government would do well to heed the advice of experts and ban tobacco promotion in all its forms. J S MINDELL D L COHEN

Headington, Oxford OX3 OBU 1 Amos A. Selling tobacco to children. BM3' 1990;301:1173-4. (24 November.) 2 Committee for Monitoring the Agreement on Tobacco Advertising and Sponsorship. Third annual report. London: HMSO, 1990.

Effect of a general practitioner's consulting style SIR,-We welcome the interest that Dr P Kinnersley and colleagues have shown in our research into general practitioner consulting styles'2 but resist their charge that our study did not allow us to conclude that patients may prefer a directing style from their general practitioner for some problems. There is widespread agreement that consulting style is likely to affect the outcome of a consultation but the conventional wisdom, to which we subscribed, holds that a sharing style produces better results. This common view is, however, based more on frequency of assertion rather than on empirical findings. Indeed, references quoted by Dr Kinnersley and colleagues, such as McWhinney's textbook,3 use descriptive rather than experimental evidence. Henbest and Stewart's study at least attempted to approach the problem in an empirically rigorous way by analysing consultation styles of a group of Canadian doctors and related this to outcome.4 We acknowledge this as an interesting study, but this design offered no guarantee that the patients consulting each doctor were equivalent. At least in our so called "methodologically flawed" study we did offer a randomised control design. Despite our study's rigorous design there are other explanations for our findings, and we discussed these in our paper. We accept that we looked at only the concluding part of the consultation, but this was because of the ethical difficulty of randomising patients at the beginning. Others might define "directing" and "sharing" styles differently, but our operationalisation of these concepts was clearly stated. We also commented on the dangers inherent in drawing wider conclusions from the study of only one general practitioner, but we did offer a clear methodology in a field strewn with prejudice and hearsay. Conventional wisdom assumes that a sharing approach is better than a directing one-would our colleagues have put pen to paper to decry our methods had we confirmed this? Not only are we chastised for methodological failings but our paper is also "philosophically flawed," whatever this means. We would be delighted if future research showed the influence of our findings to be wrong, but we continue to believe that the only way of achieving a better understanding of this important facet of every doctor's work is further empirical study along the lines we have described, particularly in exploring the type of problem that might benefit from a particular style. RICHARD SAVAGE DAVID ARMSTRONG Stockwell Group Practice, London SW9 OUB 1 Kinnersley P, Owen P, Richards J, Wilkinson C. Effect of a general practitioner's consulting style. BMJ 1990;301:1218. (24 November.) 2 Savage R, Armstrong D. Effect of a general practitioner's consulting style of patients' satisfaction: a controlled study. BMJ 1990;301:968-9. (27 October.) 3 McWhinney IR. A textbook offamily medicine. Oxford: Oxford University Press, 1989:111-52. 4 Henbest RJ, Stewart M. Patient-centredness in the consultation. 2: Does it really make a difference? Fam Pract 1990;7:28-33.

BMJ VOLUME 302

19 JANUARY 1991

Selling tobacco to children.

pathy ... lest the term delude us into thinking that we understand what is going on." If increased capillary pressure is essential for red cell extrav...
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